ABINITIO CALCULATIONS ON METHANE INTERACTING WITH THE 14-ELECTRON NI(PH3)2 FRAGMENT

Ab initio restricted Hartree-Fock and configuration interaction calculations have been carried out on the system Ni(PH3)2 + CH4 in order to study the energetics and the mechanism of the oxidative-addition reaction of CH4 and to model the activation of the C-H bond by zerovalent, co-ordinatively unsaturated transition-metal complexes. Energy-gradient optimizations and transition-state localizations have been performed on reactants and products in various constrained geometries. The results indicate that the oxidative addition of methane to Ni(PH3)2 is endothermic by 7.0 kcal mol-1 and the planar trans product is the most stable, being lower in energy than the cis isomer by 3.4 kcal mol-1.